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heat sink problem

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I know that I can read RPi temperature through console, but I’d like to measure it using a standard, hardware thermometer. Is this possible?

Can I attach thermocouple directly to the RPi’s processor as shown in the below pictures:

enter image description here enter image description here

Or am I risking some electrical problems on can endanger my device in any other way?

 New contributor
  • Hi @trejder, Ah, let me see. It depends on the thermocouple. My industrial grade pt100 should be OK, at least for hobbyist’s Micky Mouse projects: WZP pt100 Platinum Thermistor, Temperature Sensor Datasheet – MicroSensor microsensorcorp.com/upload/article/171012/… – tlfong01 15 hours ago    
  • No, my thermocouple isn’t anyway that advanced as yours! :> As you can see on the photos above, it is nothing else than an isolated wire with a metalic ending, attached to a small, batter-powered thermometer. – trejder 15 hours ago
  • What purpose does that achieve? Use vcgencmd measure_temp to get the CPU/GPU temperature from the built-in sensor. – Dougie 13 hours ago
  • @Dougie I thought that reasons are quite obvious: (a) because this way I can read the temperature (bit smaller, but still close to the real one) without using a computer or any other electronic device (by simply looking at my thermometer display), (b) because this way I can read outer temperature of the processor as addition or as a compare to console information, showing inner temperature of the processor and (c), because this way I can read temperature of radiator, if I decide to replace my fan with the radiator, again for compare reasons. – trejder 12 hours ago
  • That’s not what I mean. What does knowing the temperature tell you? What can you do about it (apart from nothing)? Even vcgencmd measure_temp doesn’t tell you much that’s useful. – Dougie 12 hours ago

3

There’s nothing wrong with putting a thermocouple on the chip heatsink like this. You can still damage the Pi if the rest of your setup is inappropriate: for instance if your thermocouple wiring is exposed to ESD or it is powered by a non-isolated power supply (though in the latter case I would worry about my own health more).

If the temperature sensor is connected to a battery-powered equipment (a multimeter) or to equipment powered by a class II power supply (⧈), you should be fine.

You won’t get much precision unless you provide a good thermal contact with the chip (thermal paste), and you should still expect a difference of some 2..10 degrees between the temperature inside and outside the chip (inside is hotter).

  • Thank you. Exactly as you said in second paragraph, my thermocouple is connected to a small, battery-powered thermometer. I have some doubts if moving RPi around a little bit won’t cause thermocouple to slip from the heatsink and touch any element on the main board? My friend told me to avoid this by gluing thermocouple to the processor with a hot-temperature glue, which itself is an electric isolation. – trejder 15 hours ago
  • 1
    Touching elements on the main board (or the pins) is indeed a risk, so if you plan to do the measurement for more than a minute, you should glue it or otherwise mechanically secure it. The thermocouple itself connecting to something shouldn’t be a problem, the problem is that it’s big enough to short two points together. – Dmitry Grigoryev 15 hours ago
  • As you can see in my other question the difference is between 5-6 degrees when thermocouple is attached to the plastic case of RPi (as currently). So I assume that when attaching it directly to heatsink the differences will be a bit lower. – trejder 15 hours ago
  • I have a bad feeling that (due to my not-so-good English) we misunderstood each other. I am asking about attaching a thermocouple directly to the processor. Notice that there is no heatsink in between (unless there’s something built-in by default). I only consider purchasing a separate heatsink, but right now this is a pure processor. Does this change anything? – trejder 12 hours ago
  • @trejder No, I think we’re talking about the same thing. I called the metal slab on top of the chip a “heatsink”. I’m not sure how it is really called, maybe a heat-spreader or something. It’s indeed built-in in the sense that the chip comes with it and you shouldn’t try to remove it. – Dmitry Grigoryev 12 hours ago

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